The objective of this research is: a) to isolate cell lines that fail to process or degrade their RNA; b) to identify ribonucleases in the nucleus and cytoplasm of an established cell line; c) to allocate physiological functions to various ribonucleases; d) to find the function of poly (A) in messengers; e) to understand the process of heterogenous RNA turnover in the nucleus; f) to comprehend the process of rRNA turnover. These objectives will be pursued by a combination of physiological, biochemical and genetical analyses. For the analysis of these problems some established techniques and some new techniques will be used. In order to identify the ribonucleases and other enzymes of interest, proteins from the nucleus and cytoplasm will be assayed in a variety of ways for the ability to degrade specifically unique polyribonucleotides such as single stranded, double stranded and RNA in RNA-DNA hybrids. For this purpose a new technique, chromatography of ribonucleases on single stranded DNA agarose columns, will be employed. In order to isolate mutants in the various processes outlined, mutagenized cells will be grown in multiwell plates and labeled with radioisotopes and mutants that would fail to degrade or synthesize specific RNA molecules under defined set of conditions will be looked for by means of autoradiography. On the other hand mutants that fail to show a specific ribonuclease function will be looked for by using the same multiwell plates. RNA metabolism in the parental and derived mutant lines will be studied. Thus an understanding of some critical events in RNA metabolism in the nucleus and the cytoplasm of established cell lines will be obtained and a basis for comparison of RNA metabolism in malignant transformed lines and their parental nontransformed cell lines will be established.